Prince William and Kate Middleton married at Westminster Abbey in a sumptuous show of British pageantry that attracted a huge world audience and breathed new life into the monarchy.

One million well-wishers watched military bands in black bearskin hats and household cavalrymen in shining breastplates escorting the beaming couple in a 1902 open-topped state landau carriage after the ceremony.

The newly-weds then appeared on the balcony of the Queen's Buckingham Palace where they sealed their union with two kisses before a jubilant, cheering crowd who waved flags and banners.

"The monarchy is like our Hollywood, the movies, for us," said Californian Diane Weltz, who treated her daughter Samantha to a trip to London for her 21st birthday.

The 29-year-old, whose mother's family has coal mining roots, has brought a sense of modernity to the monarchy and helped restore popularity to an institution tarnished by the death of William's hugely popular mother Princess Diana in 1997.

Fans from Asia to the United States camped overnight outside the abbey to catch a glimpse of the future king and queen, whose marriage has fuelled a feel-good factor that has briefly lifted Britain from its economic gloom.

More than 8000 journalists descended on London and the ceremony was streamed live on YouTube, ensuring what experts expect will be one of the biggest global audiences ever.SEALED WITH KISSES

The crowd entered into the festive spirit on a day when threatened rain failed to materialise by wearing national flags, masks of the couple and even fake wedding dresses and tiaras.

"It should have been me!" shouted nurse Jo Newman, 27, dressed as a bride and clutching a bouquet of plastic roses.

Hundreds of police officers, some armed, dotted the royal routes in a major security operation. Plain clothes officers mixed with the masses who were packed behind rails to watch the couple seal their marriage with one sheepish kiss, then another.

World War Two and modern warplanes flew over the waving royals before they headed inside for a champagne reception for 650 guests in the palace's 19 opulent state rooms.

The couple made a surprise appearance in an open-top vintage Aston Martin owned by the prince's father with the licence plate "JU5T WED" trailing balloons to travel the short journey to St James's Palace in another informal and crowd-pleasing gesture.

They will return to Buckingham Palace for a more intimate dinner and party for 300 close friends and family.

Their honeymoon starts tonight (NZ time) and the venue has been kept virtually a state secret. When that is over, speculation is bound to turn to when Middleton becomes pregnant.

The exuberance of royal fans was not shared throughout Britain. For some, the biggest royal wedding since Diana married Charles in 1981 was an event to forget, reflecting divided opinion about the monarchy.

In the economically depressed northern city of Bradford, for example, businessman Waheed Yunus said: "It's two young people getting married. It's as simple as that. It happens throughout the whole world every single day.

"There are much more pressing issues. There are much more important things going on in the world."

The marriage between William, 28, and Middleton, dubbed "Waity Katie" for their long courtship, has cemented a recovery in the monarchy's popularity.

A series of scandals involving senior royals, Britain's economic problems and Diana's death after her divorce from Prince Charles led many to question the future of the monarchy.

But Middleton's background, William's appeal, the enduring adoration for his mother and a more media-savvy royal press team have helped to restore their standing with the wider public.

A Daily Mail survey showed 51 per cent of people believed the wedding would strengthen the monarchy in Britain, compared with 65 per cent who said the marriage between Prince Charles and divorcee Camilla Parker Bowles in 2005 would weaken it.

However, while Queen Elizabeth, 85, exercises limited power, and is largely a symbolic figurehead in Britain and its former colonies, critics question the privileges she and her family enjoy, particularly at a time when the economy is so weak.

The monarchy officially costs the British taxpayer around £40 million (NZ$82.5m) a year, while anti-royalists put the figure at closer to £180 million (NZ$371m).

DRESS DESIGNER UNVEILED

Middleton's dress, the subject of fevered speculation for months in the fashion press, was a traditional ivory silk and satin outfit with a lace applique and flowing train.

It was designed by Sarah Burton of the Alexander McQueen label, named after the British designer who committed suicide.

The bride wore a tiara loaned by the queen and the diamond and sapphire engagement ring that belonged to Diana, who was divorced from Prince Charles in 1996, a year before her death in a car crash in Paris aged just 36.

The royals' cool reaction to Diana's death contrasted with an outpouring of public grief and marked a low point for the family. Some questioned whether the institution, a vestige of imperial glory, had outlived its unifying role in a modern state divided by partisan politics and regional separatism.

About 5500 street parties will be held across Britain, in keeping with tradition, although they will be more common in the more affluent south of England than in the poorer north.

Bells pealed loudly and trumpets blared as 1900 guests earlier poured into the historic abbey, coronation site for the monarchy since William the Conqueror was crowned in 1066. The abbey's bells will ring out for three full hours.

The queen, other royals, Prime Minister David Cameron, David and Victoria Beckham, the footballer-pop star couple, and singer Elton John were among famous guests at the abbey. Elton John sang "Candle in the Wind" at Diana's funeral in the abbey.

They joined 50 heads of state as well as friends, charity workers and war veterans who know the prince from his military career in what commentators said was a more progressive snapshot of modern Britain than previous royal weddings.

Middleton has been given the title Her Royal Highness, The Duchess of Cambridge, after the queen made her grandson William the Duke of Cambridge to mark the marriage.

William could face a long wait for the throne. His grandmother Queen Elizabeth shows little sign of slowing down at 85 and his father Charles is a fit and active 62-year-old.